Calcium (Ca) and dysprosium (Dy) co - doped spinel zinc ferrite: Synthesis, multifunctional properties and its applications

This work is aimed to modify the properties of zinc ferrite (ZnFe2O4) by introducing 5 %, 10 % and 15 % calcium (Ca) and dysprosium (Dy) each in host lattice. Accordingly Ca and Dy co - doped zinc ferrite nanoparticles with general formula CaxZn1-xDyxFe2-xO4 (x = 0.0, 0.05, 0.10, 0.15) were synthesized by chemical co-precipitation technique using oleic acid as surfactant. The structure was found to be face centred cubic spinel with Fd3m space group as revealed by powder X -ray diffraction. The crystallite size determined in the range 26 - 17 nm decreases whereas lattice parameter increases with increase in 'x'. Morphological analysis by high resolution scanning electron microscopy shows decrease in agglomeration with increase in doping concentration. The presence of all essential elements was confirmed by energy dispersive X -ray spectra. The optical band gap which increases slightly from 1.84 eV for x = 0.0 to 2.10 eV for x = 0.15 suggests that materials could be good photo catalysts for removing organic contaminants from water. Electron paramagnetic resonance spectroscopy was employed to observe the paramagnetic response. Lande g - factor values determined in the range 2.00 - 2.014 confirms the presence of unpaired electrons in the system. Increase in peak to peak line width (Hpp) from 342 G to 477 G for x = 0.0 to 0.15 respectively suggests decrease in super-exchange interactions. Narrow hysteresis loops obtained by vibrating sample magnetometer (VSM) depicts ferrimagnetic and soft magnetic behavior. Decrease in saturation magnetization (MS) with increase in 'x' is related to decrease in A - B type super-exchange interactions. Very small values of retentivity (MR) and coercivity (HC) suggests that prepared nanoparticles are super-paramagnetic. Increase in HC with increase in 'x' is attributed to increase in crystalline anisotropy. The behavior of frequency and temperature dependent dielectric constant as well as frequency dependent dielectric loss has been explained on the basis of Maxwell - Wagner model and Koop's theory.